1. Field of the invention
The invention relates to methods for automatically feeding work stations, more particularly to methods in which said feeding is performed by a robot. The invention also relates to apparatuses for practising these methods.
2. Description of the prior art
The automatic feeding of work stations is more and more frequently realized with the aid of robots. In the known methods and apparatuses in this field, the workpieces to be processed are grasped directly by a robot one after the other and conducted from a charging station to a work station, where the robot successively deposits the workpieces of a series in a holding device of the work station. The holding device provided at the work station comprises gripping and positioning means capable of strongly holding the workpieces in a precise position. At the end of processing a workpiece the work station releases this workpiece; the robot retakes it and possibly conveys it to another work station, before conducting the processed workpiece to a discharging station.
According to the nature of the workpieces to be processed and to the arrangement of the holding device of the work station, which must especially be designed to receive these workpieces, it may be uneasy to adjust a robot so that it presents the workpieces to be processed to the holding device of the work station in the exact position for the processing to be carried out, in particular when this position must be very precise. Moreover, such a holding device can receive the workpieces to be processed only in a well determined orientation so that, in principle, only one and the same face of the workpieces will be exposed to the processing means of the work station. If the workpieces are to be processed on different faces, which can possibly be located all round the workpieces, the latter must be conducted successively to different work stations, thus necessitating an equipment that is both bulky and costly, often slowing production.
The most serious inconvenience of the known methods and apparatuses appears when the work station forms part of a machine tool processing by means of cutting tools which produce chips. In such cases, the holding devices above mentioned are obviously located in the chip flow. Although evacuation jets for the chips are provided with the last mentioned type of working stations, these jets do not always eliminate all the chips from the holding devices. Now, it will be observed that the presence of only one chip in the holding device leads to a wrong position of the workpiece set therein and consequently to a perturbation of the processing.